Facioscapulohumeral muscular dystrophy is a disorder characterized by muscle weakness and wasting (atrophy). This condition gets its name from the areas of the body that are affected most often: muscles in the face (facio-), around the shoulder blades (scapulo-), and in the upper arms (humeral). The signs and symptoms of facioscapulohumeral muscular dystrophy usually appear in adolescence. However, the onset and severity of the condition varies widely. Milder cases may not become noticeable until later in life, whereas rare severe cases become apparent in infancy or early childhood. Weakness involving the facial muscles or shoulders is usually the first symptom of this condition. Facial muscle weakness often makes it difficult to turn up the corners of the mouth when smiling, drink from a straw, or whistle. Weakness in muscles around the eyes can prevent the eyes from closing fully while a person is asleep, which can lead to dry eyes and other eye problems. For reasons that are unclear, weakness may be more severe in one side of the face than the other. Weak shoulder muscles tend to make the shoulder blades (scapulae) “stick out” from the back, a common sign known as scapular winging. Weakness in muscles of the shoulders and upper arms can make it difficult to raise the arms over the head or throw a ball. The muscle weakness associated with facioscapulohumeral muscular dystrophy worsens slowly over decades and may spread to other parts of the body. Weakness in muscles of the lower legs can lead to a condition called foot drop, which affects walking and increases the risk of falls. Muscular weakness in the hips and pelvis can make it difficult to climb stairs or walk long distances. Additionally, affected individuals may have an exaggerated curvature of the lower back (lordosis) due to weak abdominal muscles. About 20 percent of affected individuals eventually require the use of a wheelchair. Additional signs and symptoms of facioscapulohumeral muscular dystrophy can include mild high-tone hearing loss and abnormalities involving the light-sensitive tissue at the back of the eye (the retina). These signs are often not noticeable and may be discovered only during medical testing. Rarely, facioscapulohumeral muscular dystrophy affects the heart (cardiac) muscle or muscles needed for breathing.

How common is facioscapulohumeral muscular dystrophy?

Facioscapulohumeral muscular dystrophy has an estimated prevalence of 1 in 20,000 people.

What are the genetic changes related to facioscapulohumeral muscular dystrophy?

Facioscapulohumeral muscular dystrophy results from a deletion of genetic material from a region of DNA known as D4Z4. This region is located near one end of chromosome 4. The D4Z4 region normally consists of 11 to more than 100 repeated DNA segments, each of which is about 3,300 DNA base pairs (3.3 kb) long. However, in people with facioscapulohumeral muscular dystrophy the D4Z4 region on one copy of chromosome 4 is abnormally short, containing between 1 and 10 repeats. It is uncertain how a shortened D4Z4 region causes progressive muscle weakness and wasting. Researchers have proposed several possible mechanisms, but none have yet been proven. It appears that the D4Z4 region influences the activity of other genes located nearby on chromosome 4. An abnormally short D4Z4 region may somehow disrupt the normal regulation of these genes. However, it is unclear which genes are influenced by D4Z4 and what role, if any, those genes play in muscle cells. Researchers suspect that genetic factors other than the shortened D4Z4 region may also be involved in facioscapulohumeral muscular dystrophy. Read more about chromosome 4.

Can facioscapulohumeral muscular dystrophy be inherited?

This condition is inherited in an autosomal dominant pattern, which means one copy of the shortened D4Z4 region in each cell is sufficient to cause the disorder. In most cases, an affected person inherits the deletion from one affected parent. Other people with facioscapulohumeral muscular dystrophy have no history of the disorder in their family; these cases are described as sporadic and are caused by a new (de novo) D4Z4 deletion on one copy of chromosome 4.

Where can I find information about treatment for facioscapulohumeral muscular dystrophy?

What if I still have specific questions about facioscapulohumeral muscular dystrophy?

• See How can I find a genetics professional in my area? in the Handbook.
• Ask the Genetic and Rare Diseases Information Center .
• Submit your question to Ask the Geneticist .

Where can I find general information about genetic conditions?

The Handbook provides basic information about genetics in clear language.
• What does it mean if a disorder seems to run in my family?
• What is a chromosome?
• Can changes in the number of chromosomes affect health and development?
• Are chromosomal disorders inherited?
These links provide additional genetics resources that may be useful.
• Genetics and health
• Resources for Patients and Families
• Resources for Health Professionals

What glossary definitions help with understanding facioscapulohumeral muscular dystrophy?